Solvent extraction of rare earth elements and α-alumina production from pregnant leaching solution obtained from Turkish bauxite-related ore

The use of bauxite-related shales as a secondary source for the extraction of rare earth elements (REEs) is very important to meet the raw material supply, which is the keystone of advanced technology applications. This study presents the investigation into the recovery of REEs from Kızıldağ shale ore and the potential utilization of its leach residue as a silica source. Mineralogical analysis revealed that the ore predominantly consists of paragonite, muscovite, quartz, pyrophyllite, and calcite. Calcined ore was subjected to acid leaching, and the resulting pregnant solution was purified using solvent extraction to separate from aluminum the ∑REEs with a content of 1887.35 ppm. Optimal solvent extraction conditions 1.5 M D2EHPA, 50% O/A ratio, pH 1.5, and 15-minute mixing time achieved 95% total REE extraction, with efficiency in the order Pr > La > Nd > Ce > Dy > Y > Sc. To purify Al from the Fe- and K-rich solution post-SX, electrolysis was performed, resulting in 97.16% precipitation efficiency of Al as Al(OH)3 at pH 5. The precipitate was subsequently roasted at 1100°C to produce α-alumina with 75.2% Al2O3 content. These findings confirm the technical feasibility of recovering REEs and producing coarse-purity alumina from Kızıldağ shale ore.